Summary: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 21, NO. 3, JUNE 2011 709
Superconducting RF Metamaterials Made With
Magnetically Active Planar Spirals
C. Kurter, A. P. Zhuravel, J. Abrahams, C. L. Bennett, A. V. Ustinov, and Steven M. Anlage
Abstract--Superconducting metamaterials combine the advan-
tages of low-loss, large inductance (with the addition of kinetic in-
ductance), and extreme tunability compared to their normal metal
counterparts. Therefore, they allow realization of compact designs
operating at low frequencies. We have recently developed radio fre-
quency (RF) metamaterials with a high loaded quality factor and
an electrical size as small as 658 ( is the free space wave-
length) by using Nb thin films. The RF metamaterial is composed of
truly planar spirals patterned with lithographic techniques. Linear
transmission characteristics of these metamaterials show robust
Lorentzian resonant peaks in the sub-100 MHz frequency range
below the of Nb. Though Nb is a non-magnetic material, the
circulating currents in the spirals generated by RF signals produce
a strong magnetic response, which can be tuned sensitively either
by temperature or magnetic field thanks to the superconducting
nature of the design. We have also observed strong nonlinearity